Chemical vapor deposition reactors for processing semiconductor wafers are well known in the art. For example, Yamazaki, et al., U.S. Pat. No. 4,105,810, issued Aug. 8, 1978 which is incorporated herein by reference shows in FIGS. 3a, 3b and 3c three configurations of reactors and nozzles for performing chemical vapor deposition on a semiconductor substrate. None of these reactors or nozzle designs completely solves the problem of depositing a CVD coating on a wafer so that the wafer has a uniform thickness. In fact, the problem of achieving a coating of uniform thickness over the entire surface of a wafer has become more acute and more difficult as semiconductor wafers have increased in size (diameter). In turn, the proposed solutions to the problem have become more complex. For example, with a view to improving uniformity, Yamazaki et al. supra states that it is preferred to impart a rotational or reciprocating movement to the nozzle within the reaction chamber or to the substrate (see column 6, lines 17-19). However, in addition to introducing problems of reliability, such moving parts themselves tend to introduce undesirable particulate contamination without in fact solving the problem of uniform deposition.